This invention relates to a motor control system for a telescope usable in controlling the position of the viewing assembly or telescope tube in the telescope. The invention is particularly applicable to a control system for making adjustments in the declination of the viewing assembly of the telescope, although in disclosing the invention in the context of declination adjustments, it is not intended to preclude the application of the invention toward the making of other adjustments in the telescope where smooth, vibration-free operation is desired.
A common form of mounting system for an astronomical telescope embodies a two axes system having an inclined rotation axis which parallels the earth's rotation axis and a second horizontal rotation axis which intersects the inclined axis at right angles to a vertical plane containing the latter axis. The inclined axis is referred to as the polar axis of the telescope and the horizontal axis is referred to as the declination axis. Rotation of the telescope tube about the declination axis adjusts the elevation of the telescope tube to correspond to the latitude at which the telescope is used. Rotation of the telescope tube about the polar axis moves the telescope tube in a rotary tracking motion.
Adjustments in declination are generally accomplished utilizing a knob attached to a lead screw which operates a tangent arm connected to the viewing assembly or telescope tube in the telescope. Such adjustments may be done manually, however, an electric motor facilitates this adjustment, especially when used with video cameras where smooth vibration-free operation is imperative. Whenever a telescope is used with a time exposure camera, it is absolutely necessary to have a motor operate the lead screw since the slightest touch of the hand to the telescope would ruin the picture due to the high magnification.
A number of suppliers produce motor systems for controlling declination, but those known to me have been subject to a number of shortcomings. Most use pulleys and rubber belts which interconnect a motor with the lead screw in the declination control system, and such assemblies tend to give backlash and not be dependable, with the most frequent complaint being that the belts fall off and are hard to find in the dark. Declination motors that use belts also require that the user drill holes in the telescope frame to attach the motor, and with the motor attached, such motor protrudes so far that the telescope will not fit in the case which is provided for carrying the telescope. Gear systems have also been suggested, but these tend to be expensive, and since the gears in the system are small, malfunctioning due to slipping or binding frequently occurs.
A general object of this invention is to provide a motorized drive attachment for installation with a rotatable control shaft of a telescope which is easily installed, simple in operation, and which is free of the general problems characterizing existing systems.
More specifically, an object is to provide such a motorized drive attachment which provides direct coupling of a motor in the attachment with the telescope control shaft with the elimination of gears or drive belts.
A related object is to provide such a drive attachment which includes a coupler connecting the drive shaft of the motor with the control shaft of the telescope, the coupler including a socket opening lined with an annular elastomer drive member, which may be, for instance, an O-ring, which establishes a driving connection between the coupler and the control shaft. With the attachment mounted on the telescope and coupled to one end of a control shaft, such as a rotatable declination shaft which has a knob on its opposite end for manual control, the annular drive element may also function as a clutch accommodating slipping within it of the declination shaft when the declination shaft is turned manually by the knob on its opposite end.
The drive attachment further features a novel releasable clamp structure with flexible and resilient clamps which move into a seated position on the frame of the telescope with the attachment in place. The attachment is readily mounted and demounted from the telescope frame in the dark and under conditions of field use.